Table 2. tRNA decoding and reading frame maintenance for 4-fold degenerate codonsa.
| tRNA/ASL and anticodon | Relative codon bindingb | Modification(s) present | Restored codon bindingb | Translocationc | Frameshiftingd | ||
|---|---|---|---|---|---|---|---|
| Unmodified | Modified | ||||||
| Arg CCG | CGG | CGA | s2C32; m1G37 | CGG/A | G37: CGG | ||
| – | ND | ND | |||||
| Arg ACG | CGU | CGC | |||||
| – | ND | ||||||
| Pro UGG | CCA | CCG | Um32; cmo5U34; | CCA/G/U/C | G37: CCA/G and | ||
| ++++ | – | m1G37; Ψ40 | ND | CCU/C | |||
| Ser UGA | UCA | UCU | |||||
| +++ | + | ||||||
| UCC/G– | |||||||
| Val UAC | GUA | GUG | cmo5U34 | GUA | GUG/U | cmo5U34: | |
| +++ | + | +++ | – | GUA/G/U | |||
| GUU | GUC | GUG ++ | ++++ | ||||
| – | ND | GUU ++ | |||||
| Ala UGC | GCA– | GCG– | |||||
| Leu | CUU/C | CUA/G | m1G37; Ψ38–39 | CUU/C/A/G | G37: CUU/A/G | ||
| ND | ND | ND | (CUC in P-site) | ||||
| U38–39: CUU, | |||||||
| CUA/G | |||||||
ND, not determined.
aAminoacyl- (A-) site and peptidyl- (P-) site ribosome binding by anticodon stem and loop domains (ASL) not previously reported were accomplished according to published methods (92–94). Translocation of ASLs from the A- to the P-sites was accomplished with published methods (67). Published results are from references 94,96,123–125.
bRelative codon binding relates binding affinity to that of fully modified tRNA or ASL: ++++ equals tRNA or fully modified ASL (Kd ∼ 100 nM); –, no binding (Kd > 2000 nM).
cTranslocation for ASLVal normalized to ASLVaUAC with cmo5U34.
dFrameshifting by hypomodified tRNA having the noted modifications and on the specified codons in mutant cells relative to fully modified tRNA in wild-type cells.